The recycling of wine barrels is common practice within the wine industry. Reusing barrels is one of the ways that wineries can reduce their overheads. This is especially true in large wineries where multiple hundreds of barrels are in circulation at any one time. Barrels have a limited life and are only able to be cleaned a certain number of times. To extend the life of a barrel, it is first used for white wines, cleaned and then used for red wines. The time that the wine spends in a particular barrel depends on the type and quality of the wine that is being produced.
The wood of a new barrel imparts the most flavour into the wine, with the effect being diminished with each re-use of the barrel. Therefore since new barrels are expensive their initial use is normally reserved for premium wines. The third use of a barrel usually doesn't add much flavor to the wine. For this reason many producers manage their barrels carefully, ageing their wine in a mix of new and used barrels to avoid over-oaking the wine. Care however must be taken in the use of older barrels, since the interior can harbor bacteria and yeasts that might contaminate the wine that is to be placed in the cleaned barrel. Such contamination costs the wine industry vast amounts each year in spoilt wine. Furthermore, the winemaker will not know whether a wine has been spoilt until it has spent some time in the barrel.
In order to overcome this problem, the inner surface of the wine barrel is often shaved to remove wine residues. Various apparatuses including cutting routers, planes and rotating wire brushes have been used to remove a small amount of wood off the inner surface of the barrel's staves. The process involves either the dismantling of the barrel or the removal of one end of the barrel. The wood of the interior of the barrel is then shaved to remove residues. Shaving the wood reduces the chance of contaminating the wine that is to be placed in the barrel at a latter time. The method however is not time effective since the barrel must be moved to a location where it can be shaved. Furthermore the inner surface of the barrel must be re-toasted.
Other methods used for decontaminating a barrel involve the use of high-pressure hot or cold water or steam to clean the interior surface of the barrel. A high-pressure water or steam lance is inserted through the bunghole and is manually manipulated or rotated to spray jets of water or steam over the internal surface of the barrel. This loosens the wine residue, tartrates and the like which can then be removed. The detritus can then be drained by the use of a pump or by inverting the barrel.
An alternate method that is used involves inverting the barrel over a cleaning nozzle that sprays high-pressure hot or cold water or steam over the interior surface of the barrel. The advantage of using steam or high-pressure hot water to clean the residue from the interior surface is that it also disinfects the surface. However, both methods of using steam or water are limited because they require the application of the steam or water to occur directly on the inner surface of the barrel. This poses problems especially around the bunghole, as it is difficult to rotate the nozzle to a position where the surface is directly contacted by the steam or water. Furthermore these methods often require a large amount of water and power, as the water needs to be heated.
Throughout this specification, the term sonotrode is used to describe a component that transmits ultrasonic vibrations produced from a transducer to the material to be sonified.